To edit a Legacy Agency's fee, navigate to the Active Agencies section of your Agencies page. Click on the Actions Menu for the agency you want to edit and select "Edit Fee".
Modify the agency fee to what you want the agency to earn. Note you will pay an additional 1% processing fee, thus what "You Pay" is also shown. When the fees are what you want click "Update Fee". The agency will also be notified of the change in fee.
You can also edit a Legacy Agency's fee via the menu on the Agency Profile Card and selecting "Edit Fee".